On Thu, Oct 18, 2018 at 10:12 AM, Sven R. Kunze wrote:
> On 18.10.18 18:49, Anders Hovmöller wrote:
>
>> If it's AND, shouldn't it be "hasinterfaces" (notice the s!)?
>
>
yeah, that would make sense.
Is someone proposing something here? The point I was making, is in the case
of ABCs:
issubclass
> Does AND even make sense for isinstance/issubclass?
Why wouldn't it? Python supports multiple inheritance.
/ Anders
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On 18.10.18 18:49, Anders Hovmöller wrote:
If it's AND, shouldn't it be "hasinterfaces" (notice the s!)?
Yeah, could be.
To be sure, we are on the same page here: "interface" refers to a set of
attributes of the object in question, does it?
E.g. like the __iter__ iterface. I usually don't c
>> Even though, it would be the same as issubclass() (though I'd like an AND
>> relationship with the tuple of ABCs..)
>
> When "hasinterface" ANDs the tuple, it's already different, isn't it?
>
If it's AND, shouldn't it be "hasinterfaces" (notice the s!)?
One could also imagine that isinstan
On 12.10.18 01:30, Chris Barker via Python-ideas wrote:
If Python had a way to check ABCs without issubclass, then I wouldn't
care about subclasses at all. I'd actually kind of like to have:
hasinterface(an_object, (ABC1, ABC2, ABC3))
I actually like your idea and could imagine using "hasint
I think it could inherit from the Mapping abc?
class frozendict(Mapping):
def __new__(cls, *args, **kwargs):
d = dict(*args, **kwargs)
proxy = MappingProxyType(d)
instance = super().__new__(cls)
instance.__proxy = proxy
return instance
def __hash__
вторник, 16 октября 2018 г., 12:29:55 UTC+3 пользователь Steven D'Aprano
написал:
>
>
> > It seems to me that we would need this restriction to make a reasonably
> > universal frozendict that is, itself, hashable.
>
> When people talk about frozendicts being hashable, they mean it in the
> sa
On Tue, Oct 16, 2018 at 01:02:03AM -0700, George Leslie-Waksman wrote:
> Would a frozendict require that keys and values be hashable?
Keys, yes. Values, no.
If the values were hashable, the frozendict itself would also be
hashable. If not, then it would be like trying to hash a tuple with
unhas
On Tue, Oct 16, 2018 at 7:02 PM George Leslie-Waksman wrote:
>
> Would a frozendict require that keys and values be hashable?
Keys would already have to be hashable - regular dicts demand this,
and there's no reason not to for frozendict.
Values? Not so sure. Personally I would say that no, they
Would a frozendict require that keys and values be hashable?
It seems to me that we would need this restriction to make a reasonably
universal frozendict that is, itself, hashable. With this restriction for
the general case, is there still sufficient value for everyone that is
asking for a frozend
Chris Barker - NOAA Federal via Python-ideas wrote:
Or maybe come up with a new name
We should call it a birdseyedict, because of this:
http://www.vulture.com/2016/12/unearthing-a-rare-1971-monty-python-film-all-about-peas.html
--
Greg
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Python-i
On Thu, Oct 11, 2018 at 3:35 PM, Steven D'Aprano
wrote:
> On Thu, Oct 11, 2018 at 12:34:13PM -0700, Chris Barker via Python-ideas
> wrote:
>
> > I don't care what is or isn't a subclass of what -- I don't think that's
> a
> > Pythonic question. But I do think :
> >
> > issubclass(frozendict, abc.
On Fri, Oct 12, 2018 at 9:16 AM Steven D'Aprano wrote:
>
> On Fri, Oct 12, 2018 at 02:45:30AM +1100, Chris Angelico wrote:
> > On Fri, Oct 12, 2018 at 2:41 AM Chris Barker - NOAA Federal via
> > Python-ideas wrote:
> > >
> > > > This violates the Liskov Substitution Principle.
> > >
> > > If we R
On Thu, Oct 11, 2018 at 12:34:13PM -0700, Chris Barker via Python-ideas wrote:
> I don't care what is or isn't a subclass of what -- I don't think that's a
> Pythonic question. But I do think :
>
> issubclass(frozendict, abc.Mapping) and issubclass(frozendict, abc.Hashable)
>
> would be useful.
On Fri, Oct 12, 2018 at 02:45:30AM +1100, Chris Angelico wrote:
> On Fri, Oct 12, 2018 at 2:41 AM Chris Barker - NOAA Federal via
> Python-ideas wrote:
> >
> > > This violates the Liskov Substitution Principle.
> >
> > If we REALLY had a time machine, then dict would subclass frozendict,
> > and w
BTW:
In [7]: issubclass(set, frozenset)
Out[7]: False
In [8]: issubclass(frozenset, set)
Out[8]: False
no reason to do anything different here.
and:
In [13]: issubclass(MappingProxyType, abc.Hashable)
Out[13]: False
so yes, there is a need for something different
-CHB
On Thu, Oct 11, 201
On Thu, Oct 11, 2018 at 9:54 AM, Jonathan Fine wrote:
> Summary: Long post. Because of LSP, neither dict nor frozendict are a
> subclass of the other.
given Python's dynamic typing, these issues are kinda academic :-)
> Intuition tells me that a frozen dictionary is a form of dictionary
> > th
A link on https://en.wikipedia.org/wiki/Liskov_substitution_principle goes to
http://www.engr.mun.ca/~theo/Courses/sd/5895-downloads/sd-principles-3.ppt.pdf
which has a very nice example (slides 14 and 15).
Slide 14: Is immutable Square a behavioural subtype of immutable
Rectangle? And vice versa?
Summary: Long post. Because of LSP, neither dict nor frozendict are a
subclass of the other.
Chris Barker wrote:
> If we REALLY had a time machine, then dict would subclass frozendict,
> and we’d be all set.
Prediction is difficult, particularly when it involves the future. - Neils Bohr.
And be
On Fri, Oct 12, 2018 at 2:41 AM Chris Barker - NOAA Federal via
Python-ideas wrote:
>
> > This violates the Liskov Substitution Principle.
>
> If we REALLY had a time machine, then dict would subclass frozendict,
> and we’d be all set.
Thanks to virtual subclassing, we can still do this. The ques
> This violates the Liskov Substitution Principle.
If we REALLY had a time machine, then dict would subclass frozendict,
and we’d be all set.
But to what extent do we need to support ALL the ways to check for an
interface?
Personally, I think EAFTP is the most “Pythonic”, but if folks want to
ch
> https://en.wikipedia.org/wiki/Liskov_substitution_principle
> https://en.wikipedia.org/wiki/Don%27t_repeat_yourself
I did an internet search for: python liskov (over the past year).
The first result was a Ruby page (but principle probably the same)
https://www.netguru.co/codestories/solid-princ
Steve D'Aprano wrote
> Zaur Shibzukhov wrote
> > class frozendict(dict):
> This violates the Liskov Substitution Principle.
> https://en.wikipedia.org/wiki/Liskov_substitution_principle
and so, Steve said, we should not make frozendict a subclass of dict.
Perhaps Zaur was thinking of Don't Repea
On Thu, Oct 11, 2018 at 02:18:52AM -0700, Zaur Shibzukhov wrote:
>
> May be the following simple prototype of frozendict could be useful?
>
> def frozen_error():
>return RuntimeError("frozendict is not mutable")
>
> class frozendict(dict):
This violates the Liskov Substitution Principle.
May be the following simple prototype of frozendict could be useful?
def frozen_error():
return RuntimeError("frozendict is not mutable")
class frozendict(dict):
#
def __setitem__(self, key, val):
raise frozen_error()
#
def setdefault(self, key, val=None):
rais
On Thu, Oct 11, 2018 at 01:27:50PM +1100, Chris Angelico wrote:
[...]
[Cameron Simpson]
> > Well, if it were called frozendict, indeed not. It should act like dict.
> >
> > So:
> >
> > def frozendict(**kw):
> > return MappingProxyType(kw)
> >
> > You could make an argument for that (or a
11.10.18 07:20, João Santos пише:
One important difference between MappingProxyType and a "proper"
frozendict, as analog to frozenset, is that MappingProxyType doesn't
have any method to return mutated versions of itself.
MappingProxyType.copy()?
__
In tri.struct we have a class Frozen
https://github.com/TriOptima/tri.struct/blob/master/lib/tri/struct/__init__.py
that can be used to freeze stuff. I think something like this would be even
better in the standard library, especially now with data classes! If we had
this frozendict would just
One important difference between MappingProxyType and a "proper"
frozendict, as analog to frozenset, is that MappingProxyType doesn't have
any method to return mutated versions of itself.
On Thu, 11 Oct 2018 at 01:24, Steven D'Aprano wrote:
> Hi Philiip, and welcome,
>
> On Wed, Oct 10, 2018 at
That is interesting. From my recollection, when OrderedDict was
reimplemented in C, there was advice on the thread to not implement it as a
subclass of dict.
https://bugs.python.org/issue16991
I'm far from the right person to comment on the exact reasons, but perhaps
frozenset being decoupled fro
Cameron,
That's a good suggestion. Ultimately, if there are not enough various use
cases for a frozendict class, I think we could add something like this as
an example recipe similar to the recipe section in itertools. I would be
hesitant to add a quick shim to the standard library as I can't thin
On Thu, Oct 11, 2018 at 1:02 PM Cameron Simpson wrote:
>
> On 10Oct2018 20:25, Philip Martin wrote:
> >Steven, that's a great idea, and I would be 100% up for your suggestion to
> >have types.MappingProxyType renamed to frozendict.
>
> I'm not for the rename, myself. Though I'd not be against a f
On 10Oct2018 20:25, Philip Martin wrote:
Steven, that's a great idea, and I would be 100% up for your suggestion to
have types.MappingProxyType renamed to frozendict.
I'm not for the rename, myself. Though I'd not be against a frozendict
factory in builtins, a tiny shim for MappingProxyType.
It would help over using a regular dict as a default argument to a function
by preventing accidental mutation of the default or constant mapping. This
is a quickly contrived example of the convert_price function now having a
side effect by changing the translation_map.
from unicodedata import norm
Steven, that's a great idea, and I would be 100% up for your suggestion to
have types.MappingProxyType renamed to frozendict. However, the differences
in the behavior of MappingProxyType's constructor versus dict's would make
the API's behavior confusing IMO. For example, MappingProxyType(x=5, y=10
Hi Philiip, and welcome,
On Wed, Oct 10, 2018 at 12:04:48PM -0500, Philip Martin wrote:
> I generally have used MappingProxyType as a way to set default mapping
> to a function or to set an empty mapping to a function.
> I've created a gist with an example use case:
>
> https://gist.github.com
How does a frozendict help in that example? It's not obvious to me.
Despite not understanding that example, I'm +1 for having a frozendict. I
don't think it'll increase cognitive load much, as it'll sit right next to
frozenset when someone reads the builtins in alphabetical order. In my own
experi
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